The invention relates to a device for making up successive batches of articles.
The invention applies notably to the packaging of articles such as bottles, cans or pots (such as yoghurt pots), generally cylindrical in shape.
It is known that the articles are first of all routed individually on a supply track to a grouping station where the articles are formed and then spaced apart in order to be transferred to a discharge track along which they are wrapped, or packaged.
In order to form a space between two successive batches of articles, it is known that the batches can be accelerated between the supply track and the discharge track.
Distributors are at the present time seeking to reduce their stocks whilst offering ever more diversified ranges of packaged products.
As a result the throughputs of the packaging machines must be continuously reviewed upwards. Thus, in the field of the packaging of bottles or cans, at the present time throughputs of around 15,000 to 100,000 bottles per hour are being achieved.
In the known installations, the articles are grouped notably by means of grouping devices comprising gripping members driving at constant speed along a closed path.
To illustrate this type of technology, it is possible to cite notably the document GB-914 995.
These gripping members travel at a speed appreciably greater than that of the articles before they are grouped.
Because of this, the articles suffer violent impacts against the gripping members which, in the case of glass bottles, whose thickness is tending to decrease, causes a high breakage rate and limits the throughput and speed of the installation.
Devices for gripping articles are already known, which make it possible to limit the impacts, such as the one described in the document U.S. Pat. No. 5,979,147.
The device described in this document comprises a rotating disc carrying fingers coming into engagement with the articles. The articles are accelerated between the entry and exit of the device by extending the length of the fingers projecting from the disc.
This type of device does not however make it possible to appreciably reduce the impacts of the fingers against the articles. This is because, according to the number of articles per batch, the fingers will come into engagement with the articles at different points on the rotating disc so that the impact of the fingers on the articles will vary and generate a greater or lesser impact.
The invention aims to resolve notably the aforementioned drawbacks of the prior art, by proposing a device and an installation which make it possible to form batches from individual articles without causing impacts during the grouping of the articles, and which make it possible to exceed the known production rates.
To this end, a first object of the invention is a device for making up successive batches of articles, which comprises:
a supply track along which the articles are routed one by one to a supply station, at a so-called input speed which is substantially constant;
a discharge track able to receive, at a discharge station, successive batches of articles in order to route them at a so-called output speed which is greater than the input speed;
means of transferring the articles from the supply station to the discharge station, comprising a rotary member able to take and group the articles in order to form spaced-apart batches, and which comprises a succession of gripping members arranged to engage the articles at the supply station and to disengage them at the discharge station, driven continuously along a closed path, at a so-called transfer speed, greater than or equal to the input speed;
the transfer means being arranged so that the transfer speed of the gripping members is not constant, such that:
when the articles are engaged, the speed of the gripping members is substantially equal to the input speed;
when the articles are transferred, the speed of the gripping members is greater than the input speed;
when the articles are disengaged, the speed of the gripping members is substantially equal to the output speed.
The said device is characterised in that the articles are driven continuously along the said closed path on a route which follows at least a quarter of the periphery of the rotating member, so that the gripping members can come into contact with the articles and group them in successive batches, the speed of the rotating member being greater than the input speed (VE) of the articles and the rotor member making it possible to vary the number of articles per batch.
In this way, the articles are engaged gently, and then accelerated progressively, which minimises the risks of breaking and makes it possible to increase the production rates without any concerns.
Moreover, this device is quieter than the existing devices, which is due notably to the absence of impact of the gripping members against the articles.
According to one embodiment, the transfer means comprise a toothed wheel, at least part of which is mounted so as to pivot about a rotation shaft, this wheel being disposed close to the supply track and discharge track, substantially tangent to these, this wheel comprising the said gripping members.
The gripping members are for example in the form of teeth substantially regularly spaced apart, projecting radially from the toothed wheel, each tooth describing a circle passing through a first angular position in which it engages at least one article at the supply station, and a second angular position in which it disengages it at the discharge station.
The angular separation between the first and second angular positions can be between 90 and 180xc2x0, for example substantially equal to 120xc2x0.
According to one embodiment, the wheel comprises a circular fixed base and a rotating disc, both coaxial and superimposed, between which radial branches are disposed whose free ends form the said teeth.
According to a particular constructional arrangement the said branches are mounted so as to rotate on the disc by means of pivots with axes parallel to the wheel axis.
For example, each branch has a roller or a toe which cooperates with a groove provided in the base, this groove being extended in a closed loop around the axis of rotation of the wheel.
This groove is arranged so that:
when the tooth passes through the supply station, the branch which carries it pivots in the direction opposite to the rotation of the wheel so that the speed of the tooth decreases until it is substantially equal to the input speed when the articles are engaged;
between the supply station and the discharge station, the orientation of the said branch is constant with respect to the wheel, so that the speed of the tooth increases until it is substantially equal to the speed of the toothed wheel, so that the articles are grouped together in batches, accelerated and spaced apart.
According to one embodiment, the groove forms in the base a continuous cam track followed by the roller which forms the cam follower, this cam track comprising two connected portions, one of which, turned towards the supply station, has a variable curvature, and the other, turned towards the discharge station, has a substantially constant curvature, so that:
when the roller passes in the variable-curvature portion, a the branch which carries it pivots about its axis;
when the roller passes in the constant-curvature portion, the orientation of the branch is substantially constant.
The teeth comprise for example a guide surface able to cooperate with a circumference of the base.
It is also possible to provide means disposed close to the supply station, able to order and time the articles coming from the supply track, so that they have the required positioning and separation at the time they are gripped by the transfer means.
According to one embodiment, these means for ordering and timing the articles are in the form of a star wheel, mounted so as to pivot about an axis of rotation, comprising at its periphery teeth able to mesh and unmesh the articles, the teeth having housings able to receive the articles individually, the tangential speed of the said wheel being substantially equal to the input speed.
It is also possible to provide a means of driving the said star wheel and/or a means of driving the toothed wheel, connected to a control device arranged to apply to the said drive means a predetermined speed profile, chosen from amongst a preprogrammed set of speed profiles.
The or each drive means can comprise at least one motor whose rotation speed is continuously adjustable, such as an electric motor, of the brushless DC type.